What is meant by natural selection?

It is the process in which individuals whose characteristics best suit their environment are most likely to survive, reproduce and pass on the alleles for those characteristics.

A population of mice on dark volcanic rock contains both dark-furred and light-furred individuals. Explain how the population changes over many generations.

Dark mice are better camouflaged from predators, so they survive and breed more often and the allele for dark fur becomes more common.

Explain how natural selection can eventually give rise to a new species.

If two populations become separated and face different conditions, different alleles are selected in each until the two groups can no longer breed together to give fertile offspring.

Edexcel GCSE Biology 1BI0

Key Concepts in Biology

Topic overview Eukaryotic and prokaryotic cells Specialised cells and their adaptations Microscopes and magnification calculations Size, scale and units in cell biology Enzyme action and denaturation Factors affecting enzyme activity Enzymes in synthesis and digestion, and rate calculations Food tests and the energy in food Diffusion, osmosis and active transport Osmosis in potatoes and percentage change in mass

Cells and Control

Topic overview Mitosis and the cell cycle Why mitosis matters: growth, repair and cancer Growth, differentiation and percentile charts Stem cells and their use in medicine The structure and function of the brain Neurones, receptors and the reflex arc The structure and function of the eye Eye defects and how they are corrected

Genetics

Topic overview Asexual and sexual reproduction Meiosis and the formation of gametes DNA structure, genes and the genome Extracting DNA from fruit Mendel's work and the inheritance of blood groups Alleles, genotype and phenotype Monohybrid crosses and sex determination Probability and ratios from genetic crosses Causes of variation: genes and environment The Human Genome Project Genetic variation and the effects of mutation

Natural Selection and Genetic Modification

Topic overview Darwin, Wallace and the theory of evolution Natural selection and antibiotic resistance Fossil evidence for human evolution Stone tool evidence for human evolution The pentadactyl limb and the three domains Selective breeding Tissue culture Genetic engineering and modern agriculture Benefits and risks of GM organisms

Health, Disease and the Development of Medicines

Topic overview Health, disease and susceptibility Pathogens and common infections How pathogens spread, and the virus life cycle Sexually transmitted infections How plants defend themselves Physical barriers and chemical defences The immune system, immunisation and herd immunity Antibiotics and developing new medicines Aseptic technique in culturing microorganisms Testing antiseptics and antibiotics on bacterial cultures Lifestyle factors and non-communicable disease Treatments for cardiovascular disease

Plant Structures and Their Functions

Topic overview Photosynthesis as an endothermic reaction Limiting factors in photosynthesis Light intensity and the rate of photosynthesis Root hair cells, xylem and phloem Transpiration and translocation Leaf structure for photosynthesis and gas exchange Factors affecting the rate of transpiration Plant adaptations to extreme environments Plant hormones, phototropism and gravitropism

Animal Coordination, Control and Homeostasis

Topic overview Hormones, endocrine glands and homeostasis The menstrual cycle and its hormones Hormonal and barrier contraception Homeostasis and thermoregulation Controlling blood glucose, and type 1 diabetes Type 2 diabetes and body mass The urinary system and the production of urea The nephron, filtration and selective reabsorption Treating kidney failure: dialysis and transplants

Exchange and Transport in Animals

Topic overview Why multicellular organisms need exchange surfaces Alveoli and gas exchange Rate of diffusion and Fick's law The blood and its components Arteries, veins and capillaries The heart and the circulatory system Cellular respiration as an exothermic reaction Aerobic and anaerobic respiration compared Investigating the rate of respiration Cardiac output, stroke volume and heart rate

Ecosystems and Material Cycles

Topic overview Levels of organisation and interdependence Abiotic and biotic factors in a community Parasitism and mutualism Sampling with quadrats and transects Estimating population size from field data Energy transfer between trophic levels Human impact on ecosystems and biodiversity Food security The carbon cycle The water and nitrogen cycles Factors affecting the rate of decomposition Calculating the rate of decay

Natural Selection and Genetic Modification

Natural selection and antibiotic resistance

3 things to know
Paper 1

Overview

Natural selection from mutation, competition and survival of the best suited, how an advantageous allele spreads and new species form, why acquired characteristics are not selected, how antibiotic resistance and MRSA arise, finishing antibiotic courses and not prescribing them for viruses, and percentage calculations.

What you need to know

Answer each one before you reveal it.

Your recallNot started

Key term

Where does the variation that natural selection acts on originally come from?

Key term

Explain why only some individuals in a population survive long enough to reproduce.

Evaluation

Explain why an advantageous characteristic becomes more common in a population over time.

Questions from this subtopic

Each one with the model answer underneath.

1
What is meant by natural selection?
Model answer
It is the process in which individuals whose characteristics best suit their environment are most likely to survive, reproduce and pass on the alleles for those characteristics.
2
Where does the variation that natural selection acts on originally come from?
Model answer
Random mutations in DNA, which are then mixed into new combinations by sexual reproduction.
3
Explain why only some individuals in a population survive long enough to reproduce.
Model answer
More offspring are produced than the habitat can support, so individuals compete for limited food, water, space and mates.
4
Explain why an advantageous characteristic becomes more common in a population over time.
Model answer
Individuals with it survive and breed more successfully, so the allele for it is passed to a larger share of each new generation.
5
A population of mice on dark volcanic rock contains both dark-furred and light-furred individuals. Explain how the population changes over many generations.
Model answer
Dark mice are better camouflaged from predators, so they survive and breed more often and the allele for dark fur becomes more common.
6
Explain how natural selection can eventually give rise to a new species.
Model answer
If two populations become separated and face different conditions, different alleles are selected in each until the two groups can no longer breed together to give fertile offspring.

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Key Concepts in Biology

Cells and Control

Genetics

Natural Selection and Genetic Modification

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ANitrates cause an algal bloom that blocks the light.

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